Photographic monobaths containing a dl 6-8 dithio-octanoic acid antisludging agent



United States Patent M This invention relates to photographic monobaths containing an antisludging agent. i

A photographic monobath is a bath containingboth the developer and the fixer for a photographic silver halide emulsion; Typical monobath formulae are as follows:

I, grams II, grams Sodium Sulphite (anhydrous) 35 50 Hydroquimne 35 15 Sodium Hydroxide 20 5 Phenidone 1 0. 5 Sodium 'lhiosulphate Crystals 135 250 Nora-Plus water to make 1 liter, in each case.

The foregoing ingredients are typically dissolved in the water at 120 F.

If a photographic silver halide emulsion film is processed in such a monobath, in any given aliquot portion, sludge containing fixed-out silver salts, or developer oxidation products, or both, becomes plainly visible, and tends to adhere to the surface of the processed film. This difiiculty is well known.

It is the principal object of this invention to inhibit the formation of sludge in photographic monobaths during the processing therein of photographic films. It is another object of the invention to increase the quantity of photographic film that c-an be processed in a given aliquot portion of such a monobath before the onset of sludge rendering the monobath useless, that is, before the products constituting sludge are formed in such quantities that they adhere to, obscure or mar the developed image.

I have discovered that if one adds DL 6-8 dithiooctanoic acid, sometimes referred to as thioctic acid, directly or as one of several salts, to a typical monobath, as exemplified by one or the other of the foregoing monobaths, the appearance of sludge is delayed so that one can now process in a given aliquot portion of monobath up to six to twelve times the amount of photographic film that can be processed in the same aliquot portion of monobath not containing the thioctic acid.

The following examples will serve to illustrate preferred modes of practicing the invention, but are not to be construed as limiting the invention. In these examples the term thioctic acid refers to BL 6-8 dithiooctanoic acid as obtained commercially from K & K Laboratories, Inc., Long Island, NY, and listed as thioctic acid in their catalog Rare Chemicals-Fine, Catalog No. 4, copyright 1961, page 115. The chemical formula is CH, C CH(CH2)4C O OH l l Example I A solution of 1% thioctic acid in 1% sodium hydroxide Was prepared, by dissolving one gram of the acid, in the form of a white powder, in 100 cc. of a 1% solution-of sodium hydroxide. Then 10 cc. of this solution was added to one liter of a monobath made according to Formula I set forth above. In addition, one liter of the monobath was prepared, to which none of the thioctic 3,318,701 Patented May 9, 19 67 acid solution was added. In the latter monobath, development of a 7-square-inch strip of ordinary panchromatic type gelatino-silver-halide photographic film, at any temperature between approximately 20 C. and C., with processing time varying from one to ten seconds, produced a black precipitate or sludge which was plainly visible in the monobath. In the monobath to which the thioctic acid solution was added, six strips of the same film (i.e. 42 square inches) were similarly processed before a similar amount of the precipitate or sludge appeared.

. Example II The same tests as in Example I were repeated, except that 50 cc. of the thioctic acid solution was added to one liter of the monobath. This time, twelve strips of the same type of film, each having an area of 7 square inches, were processed before the sludge appeared.

Example III The tests of Example I were repeated, using Monobath Formula II instead of Formula I. The results were substantially the same as the results of Example 1.

Example IV The tests of Example II were repeated, using monobath Formula II instead of Formula I. The results were substantially the same as the results of Example II.

In each of the foregoing examples, the thioctic acid was introduced into the monobath in solution in sodium hydroxide, and hence as a sodium salt of the acid. The thioctic acid can be dissolved directly in the monobath, if desired (note that sodium hydroxide is present in the foregoing formulae). Alternatively, it can be dissolved in other solvents, such as potassium hydroxide, forming the potassium salt of the acid, or it can be introduced into the monobath as another of the alkali metal salts (e.g. ammonium), or as one of the alkaline earth metal salts (eg the barium, strontium or calcium salts) or as one of the organic salts of the acid with amines such as methylamine, ethylamine, butylamine or morpholine; olamines such as monoethanolamine, diet-hanolamine, or triethanolamine can also be used.

The proportions of thioctic acid that can be used in a given monobath will vary over a wide range. From 10 to 50 cc, of the solution of thioctic acid mentioned in the foregoing examples can be used per liter of monobath solution according to either one of Formula I or Formula II, for example. The higher proportion of thioctic acid will have a greater elfect in suppressing the formation of undesirable sludge, and will permit the processing of larger amounts of film per volume of monobath. However, a continued increase in the proportion of thioctic acid in a given monobath will eventually have the result of reducing gamma, density and speed, which is, in many cases, undesirable. Thus, a practical upper limit within which this undesirable result will not take place is: the foregoing solution of thioctic acid in sodium hydroxide should not exceed approximately 10% of the total volume of the monobath. On a weight basis, this indicates that the thioctic acid should not exceed 1% of the total ingredients (less solvent) of the monobath containing it; preferably it is a fraction of 1%.

Although certain forms of thioctic acid have heretofore been proposed for use as antif'ogging agents in photographic negative emulsions (see U.S. Patents No. 2,948,614 and No. 3,128,186), to my knowledge thioctic acid has never before been proposed in any form as an antisludging agent in a monobath. Monobaths are unique in that the tendency for fixed-out silver to form a sludge is vastly greater than in other processing solustanding deficiency of photographic monobaths.

The embodiments of the invention which have been illustrated and described herein are but a few illustrations of the invention. Other embodiments and modifications will occur to those skilled in the art. No attempt has been made to illustrate all possible embodiments of the invention, but rather only to illustrate its principles and the 'best manner presently known to practice it. Therefore, while certain specific embodiments have been described as illustrative of the invention, such other forms as would occur to one skilled in this art on a reading of the foregoing specification are also within the spirit and scope of the invention, and it is intended that this invention includes all modifications and equivalents which fall within the scope of theappended claims.

What is claimed is:

1. A photographic monobath containing phenidone, hydroquinone, sodium thiosulfate and an antisludging agent selected from the group consisting of DL 6-8 dithiooctanoic acid, alkali metal salts of DL 6-8 dithio-octanoic acid, alkaline earth metal salts of DL 6-8 dithio-octanoic acid, and amine salts of DL 6-8 dithio-octanoic acid, I

2. A-photographic monobath according to claim 1 in which the antisludging agent contains an amount of DL 6-8 dithio-octanoic acid which is a fraction of 1% of the total weight of the ingredients of the monobath.

3. A photographic monobath according to claim 1 in which the antisludging agent contains between approximately 0.1 and 0.5 gram of DL 6-8 dithio-octanoic acid per liter of monobath.

4. A photographic monobath according to claim 1 comprised of ap proximately 15% sodium sulphite (anhydrous), between approximately 5% and 15% of hydroquinone, between approximately 1.5% and 9% of sodium hydroxide, between approximately and of sodium thiosulphate, and a fraction of 1% of phenidone, by weight, and in which said DL 6-8 dithio-octanoic acid thioctic acid comprises a fraction of 1% of the total weight of the foregoing ingredients of the monobath.

References Cited by the Examiner UNITED STATES PATENTS 2,782,120 2/1957 Goldhammer et al. 9=66l 2,948,614 8/1960 Allen et al. 96-l09 3,128,186 4/1964 Corben et al. 96109 3,173,789 3/1965 King et al 96-61 NORMAN G. TORCHIN, Primary Examiner. J. TRAVIS BROWN, Examiner.

C. E. DAVIS, Assistant Examiner. 

1. A PHOGRAPHIC MONOBATH CONTAINING PHENIDONE, HYDROQUINONE, SODIUM THIOSULFATE AND AN ANTISLUDGING AGENT SELECTED FROM THE GROUP CONSISTING OF DL6-8 DITHIOOCTANOIC ACID, ALKALI METAL SALTS OF DL6-8 DITHIO-OCTANOIC ACID, ALKALINE EARTHMETAL SALTS OF DL 6-8 DITHIO-OCTANOIC ACID, AND AMINE SALTS OF DL 6-8 DITHIO-OCTANOIC ACID. 